Tancet sample questions part 3

Probability questions1. Out of 10 white, 9 black and 7 red balls, the number of ways inwhich a selection of one or more balls can be made isa. 881b. 891c. 879d. 892solution-The white balls can be selected in 10 + 1 = 11 ways.The black balls can be selected in 9 + 1 =10 ways.The red balls can be selected in 7 + 1 = 8 ways.Total number of ways = 11*10*8 = 880But this includes the case when no ball is selected.Hence the required number of ways = 880 - 1 = 879